Volume / Capacity Unit Converter
One tool for every everyday capacity / volume unit: metric (litre, millilitre, cubic metre, cubic centimetre), US customary (gallon, quart, pint, fluid ounce, cup, tablespoon, teaspoon) and imperial (UK gallon). Edit either side and the other follows; the grid below shows every unit at a glance.
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Live value in every unit
US and Imperial units follow the 1959 international yard-and-pound agreement: 1 US gal = 3.785411784 L exactly, 1 imp gal = 4.54609 L exactly (NIST Handbook 44 / UK Weights and Measures Act 1985). US tablespoon and teaspoon are exact fractions of the US fluid ounce (29.5735 mL); the everyday "1 tbsp ≈ 15 mL, 1 tsp ≈ 5 mL" labels are rounded.
- L Beverages, chemistry, fuel (metric)
- mL Medical doses, recipes, cosmetics
- gal (US) US fuel pumps and milk (1 US gal)
- gal (imp) UK / Commonwealth fuel and beer (1 imp pint = 568 mL)
- cup (US) US recipes — 240 mL (label) / 236.59 mL (exact)
- m³ Water meters, gas meters, industrial capacity
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Formula
Every unit is routed via litres: value × factor_from = litres, then litres ÷ factor_to = result.
- · 1 US gallon = 3.785411784 L exactly (NIST Handbook 44).
- · 1 imperial / UK gallon = 4.54609 L exactly (Weights and Measures Act 1985) — about 1.2× a US gallon.
- · 1 US quart = 32 fl oz = 0.946 L; 1 US pint = 16 fl oz = 0.473 L.
- · 1 US fluid ounce = 1/128 US gal ≈ 29.5735 mL; 1 US cup = 8 fl oz ≈ 236.59 mL (food labels round to 240 mL).
- · 1 US tablespoon = 1/2 fl oz ≈ 14.79 mL; 1 US teaspoon = 1/6 fl oz ≈ 4.93 mL (food labels use the rounded "1 tbsp = 15 mL, 1 tsp = 5 mL").
- · 1 m³ = 1 000 L; 1 cm³ = 1 mL (SI definition, CGPM 1964).
- · An imperial pint ≈ 568 mL — noticeably larger than the US 473 mL pint; UK pub glasses use the imperial pint.
- · Every conversion routes through litres, so there is no cascading round-off. Sources: NIST SP 811, CGPM, UK Weights and Measures Act 1985.
Frequently asked
Why do US and Imperial gallons differ — which one should I use?
The two gallons are historical: the US gallon descends from the 18th-century English wine gallon (231 in³) and was fixed by the US in 1832; the Imperial gallon was redefined by the UK Weights and Measures Act 1824 as the volume of 10 lb of distilled water, so 1 imp gal ≈ 1.20 US gal. Use US gallons for US fuel pumps, milk and soda; use Imperial gallons in the UK, Canada (historical), Australia, New Zealand and India. A bare "gal" usually means US gallons; UK / Commonwealth labels typically say "imperial gallon" or "imp gal" explicitly.
A recipe says "1 cup" — is that a US cup or a UK cup?
Most English-language recipes (US, Canadian, big publishers like King Arthur, Bon Appétit) use the US cup = 236.59 mL (commonly labelled as 240 mL). UK home cooking rarely uses "cups" — it leans on grams, pounds and millilitres instead. Australia and New Zealand adopted a metric cup = 250 mL. Some Japanese recipes use 200 mL. If the recipe does not state its origin, the US 240 mL cup is the safest assumption — and what this tool uses.
My cough syrup says "1 teaspoon = 5 mL", but the calculator gives 4.93 mL — which is right?
Both are correct: 5 mL is the metric / medical 'teaspoonful' (used by the FDA, USP and WHO). The US legal teaspoon is 1/6 fl oz ≈ 4.9289 mL — about 1.4 % less. For medication, pharmacists, nurses and labels all use a 5 mL dosing spoon because accuracy and safety matter more than the strict definition. This calculator uses the legal 4.93 mL for precise cooking conversions; for dosing, always use the 5 mL measuring cup or syringe that ships with the medicine.
How do cubic metres relate to litres, and which unit do water bills use?
1 m³ = 1 000 L; 1 cm³ = 1 mL (SI definition, 1964). Water utilities, gas meters and air-freight (IATA volumetric weight) all use cubic metres; residential water bills typically state "m³" — one m³ equals one tonne / 1 000 L. The calculator supports m³ ↔ L conversion directly, so you can read off your bill without doing the multiplication.
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